[en] Using the ARGUS detector at the e⁺e^- storage ring DORIS II at DESY the author has investigated the exclusive decays B⁰ → D*^-l⁺ν and B⁰ → D^-l⁺ν and have determined the CKM matrix element of V_cb. By measuring the yields of anti D⁰, D⁰, D^- and D*^- mesons originating from semileptonic anti B decays, the lifetime ratio of charged and neutral B mesons, τ(B⁺)/τ(B⁰), is derived. 14 refs., 3 figs

[en] Using the ARGUS detector at the e⁺e^- storage ring DORIS II at DESY we have investigated the exclusive B^→D*^-l⁺ν and B⁰→D^-l⁺v and have determined the CKM matrix element |V_cb|. By measuring the yields of bar D⁰, D⁰, D^- and D*^- mesons originating from semileptonic bar B decays, the lifetime ratio of charged and neutral B mesons, τ(B⁺)/τ(B⁰), is derived

[en] Using the ARGUS detector at the DORIS II storage ring at DESY, we have observed a charmed meson of mass (2455±3±5) MeV/c², decaying to D⁺π^-. The natural width of this state is determined to be (15) MeV/c². The fragmentation function is hard, as expected for a leading charmed particle from nonresonant e⁺e⁺ annihilation. Analysis of the decay angular distribution supports the hypothesis that the observed state is an L=1 excited charmed meson with spin-parity 2⁺. (orig.)

[en] We propose a Zernike phase contrast electron microscope that uses an intense laser focus to convert a phase image into a visible image. We present the relativistic quantum theory of the phase shift caused by the laser-electron interaction, study resonant cavities for enhancing the laser intensity and discuss applications in biology, soft-materials science and atomic and molecular physics.

[en] Using the ARGUS detector at the DORIS II storage ring we have searched for B⁰anti B⁰ oscillations in Y(4S) decays. One explicitly mixed event, a decay Y(4S) → B⁰B⁰, has been completely reconstructed. Furthermore, we observe a 4.0 standard deviation signal of 24.8 events with like-sign lepton pairs and a 3.0 standard deviation signal of 4.1 events containing one reconstructed B⁰(anti B⁰) and an additional fast l⁺(l^-). This leads to the conclusion that B⁰-anti B⁰ mixing is substantial. For the mixing parameter we obtain r = 0.21±0.08. (orig.)

[en] The detector ARGUS has been designed as a universal tool to investigate final states from e⁺e^- annihilation processes in the energy range of the Υ resonances. ARGUS started operation in October 1982 and has since successfully taken data at the Υ(1S), Υ(2S) and Υ(4S) energies, and in the nearby continuum. The detector combines excellent charged particle identification and good photon energy resolution over more than 90% of the full solid angle. A particle originating from the interaction vertex and leaving the beam tube traverses the following components: The vertex drift chamber, the main drift chamber which determines its momentum and specific ionization, the time-of-flight system through which its velocity is determined, and the electromagnetic calorimeter. Muons pass through the magnet coils and the flux return yoke and finally hit the muon chamber system which surrounds the detector. The momentum resolution of ARGUS is σ(p_T)/p_T = (0.01²+(0.009p_T[GeV/c])²)^1/2, and the photon energy resolution in the barrel shower counters is σ(E)/E = (0.072²+0.065²/E[GeV])^1/2. Combining the information from all particle identification devices, more than 80% of all charged hadrons can be recognized unambiguously. The electron-hadron and muon-hadron rejection rates are 1:200 and 1:50 respectively. (orig.)

[en] Using the ARGUS detector at the e⁺e^- storage ring DORIS II, we have observed inclusive D_S production, using the channel D_S^- → φπ^-, in decays of B mesons produced on the Υ(4S). The product of branching ratios BR(D → D_SX).BR(D_S^- → φπ^-) is (4.2±0.9±0.6)x10^-3. The D_S momentum spectrum suggests a substantial two-body component to the final states of B → D_SX decays. (orig.)

[en] The final states K_S⁰K_S⁰π⁺π^- and K_S⁰K^-+π⁰π^±, produced in two-photon reactions, have been studied using the ARGUS detector at the e⁺e^- storage ring DORIS II at DESY. The reaction γγ → K^*+K^*- has been observed for the first time. Its cross section is about eight times larger than that for γγ → K^*0anti K^*0, but it has a similar W_γγ dependence. (orig.)

[en] Using the ARGUS detector at DORIS II, the decay of F⁺→anti K^*0K⁺, and the ratio BR(F⁺→anti K^*0K⁺)/BR(F⁺→Φπ⁺) is found to be 1.44±0.37. This is a substantial rate for a decay channel which cannot proceed via a colour-favoured diagram. (orig.)

[en] Using the ARGUS detector at the e⁺e^- storage ring DORIS II at DESY, we have measured the lifetimes of the D⁰, D⁺ and D_s⁺ mesons. We find τsub(D⁰) = (4.8±0.4±0.3)x10^-13 s, τsub(D⁺) = (10.5±0.8±0.7)x10^-13 s and τsub(D_s⁺) = (5.6_-1.2⁺1.3±0.8)x10.¹³s. (orig.)